Modern endoscopes have a distal tip deflection control mechanism for facilitating guided advancing within the human body cavity and for changing the facing direction of the objective lens of the distal tip according to the position of the object sought to be observed. Such distal tip deflection control mechanism includes control wires whose distal ends are fixed to the distal tip of the endoscope. The distal tip is thus operated by controlling the proximal end of the control wires at the proximal housing of the endoscope.
The distal ends of the control wires require that they be firmly fixed to the distal tip of the endoscope so that they cannot be easily broken, and on the other hand, the mechanism for holding the wires at the tip must not increase the diameter of the distal tip. Japanese Utility Model Publication No. 3-52483 (hereinafter "the 3-52483 reference"), Japanese Patent Publication Nos. 3-72291 (hereinafter "the 3-72291 reference") and 4-10327 (hereinafter "the 4-10327 reference") are the prior art attempts to satisfy these requirements.
In the 3-52483 reference, as shown in FIG. 30 hereof, a stopper 7 is fixed to the distal ends of control wires 6 (only one is shown), and the stopper 7 is fitted and fixed within a groove 9 formed on the outer circumference of the distal tip 8. An end segment of the tubular segments of the endoscope (shown in phantom) is fitted to the rear end of the distal tip and it covers and secures the circumference of the stoppers 7 within the groove 9.
In the 3-72291 reference, as shown in FIG. 31 hereof, a stopper projection 11, laterally directed, is formed at the distal end of a control wire 10, and the distal end of the control wire 10 is fitted and fixed within a groove 13 formed on the outer circumference of the distal tip 12. An end segment of the tubular segments of the endoscope (not shown) is fitted to the rear end of the distal tip and the stopper projection 11 is hooked over the top end of the end segment.
In the 4-10327 reference, as shown in FIG. 32 hereof, grooves 15a and 15b are hollowed out of a distal tip 14. The distal ends of the control wires 16a and 16b are secured in the grooves 15a and 15b, respectively, and are secured in place by filling up the grooves 15a and 15b with wire fixing material 17.